The overall objective of the proposal is to study and compare the RNA metabolism of the rat placenta, fetus and maternal liver during the course of pregnancy. Studies will be directed toward measuring nucleolar and extranucleolar DNA dependent RNA polymerase with and without the addition of ribosomal preparations. BIBLIOGRAPHIC REFERENCES: Hayashi, T.T., Prinzo, N.: Poly(U) Polymerase Activity in the Ribosomes of the Rat Maternal Liver, Fetal Liver and Placenta During Pregnancy. (Abstract) Gynec. Invest. 6:52, 1975.